Quetistedtite near Moiitpelier, Iowa. — Kuntze. 121 
The gradual loss of water at different temperatures was 
found to be as follows: 
at 105° loss of water 21.04 per cent. 
" iio'^ " " " 25.09 per cent. 
" 130° " " " 25.88 per cent. 
u j^qo »» u u 29.94 per cent. 
"red heat" " " 32.32 per cent. 
The mineral is stable in the open dry air for about 5-6 
months, but then it begins to decompose, gets white and 
crumbling. 
K mineral which is so readily soluble in water can only be 
formed under very favorable conditions, and at this locality 
the conditions were so favorable that the mineral was deposited 
in relatively large quantities. The place was protected from 
rain by overhanging rocks and shaded by trees; for the min- 
eral decomposes readily when exposed to the direct sunlight 
for a longer time. The strata are inclined towards the bed of 
the creek, underlain by the impermeable Devonian limestone, 
so that all the percolating water has its natural outflow^ just 
at this locality, making a concentration possible. The sand- 
stone is porous and contains pyrite in an enormous quantity of 
finest scales. Percolating water and evaporization were in per- 
fect equilibre at the time of my first visit. As Dana gives 
only one other locality where this mineral occurs, Tierra Am- 
arilla, near Copiapo, Chile. I took interest to visit the I0-. 
cality again in April of this year. No trace of the mineral 
could be detected; only a small quantity of water of acid re- 
action and metallic taste was flowing out of the rock. When 
I visited the locality again in August, the deposit had reached 
its original thickness. It is the same thing as with the efflo- 
rescing salt of the desert, it comes and disappears, with re- 
spect to the season. 
The rock coated by thequenstedtite is very much decom- 
posed by the free sulphuric acid, formed by the oxidation of 
the pyrite. 
2FeS., 4- H,0 -f O., = Fe., {SOJ3 + H-'SO, 
